VIENNA — Austrian police urged Vienna residents yesterday to be on heightened alert for suspicious objects and activities as they hunted for possible associates of a suspected Islamic radical who they say might have been planning a bomb attack.

A minor was among those questioned. Briefing reporters along with other senior law enforcement representatives, KonradKogler, Austria's top security official, described him as a 14-year old who had been in contact with the main suspect arrested Friday in his Vienna apartment.

Amid the search for suspects, Vienna Deputy Police Chief Karl Mahrer told reporters that the Austrian capital would remain under increased security alert until police were satisfied that any threat of potential attacks was banished

"Look instead of looking away," he urged Vienna residents, calling on them to immediately report anything unusual that could be linked to a terrorist strike.

Separately, Interior Minister Wolfgang Sobotka told state broadcaster ORF that the arrested suspect — a 17-year-old male — has said he supports the Islamic State group. Sobotka described the suspect as having a "real communications network" and as someone with "weight" in radical circles.

A SWAT team made the arrest after what police said was a tip from a "foreign intelligence service." The youth was not identified due to Austrian privacy laws, but Interior Ministry spokesman Karl-Heinz Grundboeck said the suspect is believed to be in contact with radical "Albanian-Islamist" circles.

Another suspect thought linked to the teenager arrested in Austria was in German custody after his detention Saturday.

German news agency dpa said law enforcement officials suspected the 21-year-old of helping the Austrian plan an attack and experimenting with making explosives in the German suspect's apartment in the city of Neuss. It cited them as saying, however, that no weapons or explosives were found in a search of his apartment at the time of his arrest.

Austrian authorities said after they detained their suspect that he may have been close to carrying out an attack, with the city's subway line a potential target.

Sobotka said there were no indications that he had "concrete" plans. But the decision to indefinitely increase the presence of Vienna police at train stations and other frequented areas indicated continued concerns about what Kogler described as a "potential danger situation."

Before President Rodrigo Duterte left Thursday for his one-on-one with President Xi Jinping in Beijing, he promised to “invoke” the 2016 ruling of the Permanent Court of Arbitration at The Hague that resolved some maritime disputes between the two neighbors.

Eight warships, four aircraft and more than a thousand personnel from the US and ten Southeast Asian countries will join maritime drills kicking off Monday, as part of a joint exercise extending into the flashpoint South China Sea.

China has rejected as “unwelcome” the call of the United Kingdom, France and Germany on the South China Sea claimants to respect the arbitration ruling of 2016 and the rules-based framework laid out in the United Nations Convention on the Law of the Sea (UNCLOS).